1 Let's say you already know about the six simple machines: inclined plane, wedge, screw, lever, wheel and axle, and pulley. You've probably figured out that these six machines were invented ages and ages ago. So what has been happening since then? Did someone invent simple machine number 7, 8, 9, 10, and so on? How many simple machines do we have by now? Hundreds? Thousands?2 Let's look at a bicycle for an example. A bicycle is a much newer machine than the simple lever that a cave man used to move a big old rock, but it's not as new as, say, a laptop computer. Where does a bicycle fit into the world of machines? Well, a bicycle is not number 7, or 100, or even 1000. A bicycle is actually a combination of several of those six basic simple machines. A bicycle gear is actually a combination of simple machines all by itself. A gear is a wheel, but the teeth on the gear are little wedges. What other simple machines can you find on a bicycle?3 Gears, along with other simple machines, make up many of the machines you use every day. Some examples are the lawn sprinkler, a watch, and the gearbox in a car.